<!--
@license
Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-icon/iron-icon.html">
<link rel="import" href="../paper-behaviors/paper-inky-focus-behavior.html">
<link rel="import" href="../paper-styles/default-theme.html">

<!--
Material design: [Icon toggles](https://www.google.com/design/spec/components/buttons.html#buttons-toggle-buttons)

`paper-icon-button` is a button with an image placed at the center. When the user touches
the button, a ripple effect emanates from the center of the button.

`paper-icon-button` includes a default icon set.  Use `icon` to specify which icon
from the icon set to use.

    <paper-icon-button icon="menu"></paper-icon-button>

See [`iron-iconset`](iron-iconset) for more information about
how to use a custom icon set.

Example:

    <link href="path/to/iron-icons/iron-icons.html" rel="import">

    <paper-icon-button icon="favorite"></paper-icon-button>
    <paper-icon-button src="star.png"></paper-icon-button>

To use `paper-icon-button` as a link, wrap it in an anchor tag. Since `paper-icon-button`
will already receive focus, you may want to prevent the anchor tag from receiving focus
as well by setting its tabindex to -1.

    <a href="https://www.polymer-project.org" tabindex="-1">
      <paper-icon-button icon="polymer"></paper-icon-button>
    </a>

### Styling

Style the button with CSS as you would a normal DOM element. If you are using the icons
provided by `iron-icons`, they will inherit the foreground color of the button.

    /* make a red "favorite" button */
    <paper-icon-button icon="favorite" style="color: red;"></paper-icon-button>

By default, the ripple is the same color as the foreground at 25% opacity. You may
customize the color using the `--paper-icon-button-ink-color` custom property.

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-icon-button-disabled-text` | The color of the disabled button | `--disabled-text-color`
`--paper-icon-button-ink-color` | Selected/focus ripple color | `--primary-text-color`
`--paper-icon-button` | Mixin for a button | `{}`
`--paper-icon-button-disabled` | Mixin for a disabled button | `{}`
`--paper-icon-button-hover` | Mixin for button on hover | `{}`

@group Paper Elements
@element paper-icon-button
@demo demo/index.html
-->

<dom-module id="paper-icon-button">
  <template strip-whitespace>
    <style>
      :host {
        display: inline-block;
        position: relative;
        padding: 8px;
        outline: none;
        -webkit-user-select: none;
        -moz-user-select: none;
        -ms-user-select: none;
        user-select: none;
        cursor: pointer;
        z-index: 0;
        line-height: 1;

        width: 40px;
        height: 40px;

        /* NOTE: Both values are needed, since some phones require the value to be `transparent`. */
        -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
        -webkit-tap-highlight-color: transparent;

        /* Because of polymer/2558, this style has lower specificity than * */
        box-sizing: border-box !important;

        @apply(--paper-icon-button);
      }

      :host #ink {
        color: var(--paper-icon-button-ink-color, --primary-text-color);
        opacity: 0.6;
      }

      :host([disabled]) {
        color: var(--paper-icon-button-disabled-text, --disabled-text-color);
        pointer-events: none;
        cursor: auto;

        @apply(--paper-icon-button-disabled);
      }

      :host(:hover) {
        @apply(--paper-icon-button-hover);
      }

      iron-icon {
        --iron-icon-width: 100%;
        --iron-icon-height: 100%;
      }
    </style>

    <iron-icon id="icon" src="[[src]]" icon="[[icon]]" alt$="[[alt]]"></iron-icon>
  </template>

  <script>
    Polymer({
      is: 'paper-icon-button',

      hostAttributes: {
        role: 'button',
        tabindex: '0'
      },

      behaviors: [
        Polymer.PaperInkyFocusBehavior
      ],

      properties: {
        /**
         * The URL of an image for the icon. If the src property is specified,
         * the icon property should not be.
         */
        src: {
          type: String
        },

        /**
         * Specifies the icon name or index in the set of icons available in
         * the icon's icon set. If the icon property is specified,
         * the src property should not be.
         */
        icon: {
          type: String
        },

        /**
         * Specifies the alternate text for the button, for accessibility.
         */
        alt: {
          type: String,
          observer: "_altChanged"
        }
      },

      _altChanged: function(newValue, oldValue) {
        var label = this.getAttribute('aria-label');

        // Don't stomp over a user-set aria-label.
        if (!label || oldValue == label) {
          this.setAttribute('aria-label', newValue);
        }
      }
    });
  </script>
</dom-module>
